Everyone seems to be arguing between improving the AI or toning down the amount of barrels, but really I think both of these needs to happen. The AI needs some updating because I've seen them run through fire and acid in one go just to get a bit closer to the wizard so they can hit him, and I have seen barrels in so many random places. A caravan that was transporting alcohol when it got attacked having a single barrel of firewine sitting around? That's fine, makes sense they would have some and limiting it to only a single barrel keeps people from just nuking the entire encounter in one turn. Now if that same encounter had 3 or 4 firewine barrels, it would suddenly become an extremely short fight as a single firebolt to a barrel would basically end it.

Maybe don't tone down the amount of encounters that have barrels in them, but tone down the amount of barrels in the encounter and make sure it makes sense for them to be there. It makes sense for a merchant caravan to have some alcohol on board, but it wouldn't make sense for an oil barrel to just be sitting on the side of the road for no reason. An encounter should have 1 or maybe 2 barrels max, not 5+ barrels just sitting around.

As for the AI, they need some improvement. I can't think of a single creature that is stupid enough to just go running right into the middle of a giant pool of fire, so why does the AI just straight leroy jenkins their way through every environmental effect in the game just to hit the wizard? They need some tweaking on their targeting as well, maybe have them go after the character who is actually doing to the most damage to them or to the enemies around them rather than just running straight past the warrior who just slaughtered 3 of their friends to go flying ninja kick the wizard in the stomach? I get it, the wizard has low AC and is easier to hit, plus he can be a major threat. But unless he is actually currently posing a major threat by chucking fireballs at the enemies, then every logical thought says to target the person with the giant axe who just killed your friends and not the random dude in the back holding a stick.